The Obama administration renewed calls for Iran to free retired FBI agent Robert “Bob” Levinson, who on Tuesday reached the grim milestone of becoming the longest-held hostage in U.S. history.

Levinson, now 65, was seized in 2007 from Iran’s Kish Island, where he was researching a cigarette-smuggling case as a private investigator. Seizing on signs of a thaw in U.S.-Iranian relations, Levinson’s family in Coral Springs, Fla., has issued a flurry of public appeals for his release to newly elected Iranian President Hassan Rouhani, who’s viewed as a reformist with ambitions of moving Iran away from its pariah-state status.

The family and sympathetic lawmakers and activists have pushed the Obama administration to include Levinson’s ordeal in talks on how to bring Iran back into the international fold, starting with the landmark interim deal reached over the weekend on Tehran’s nuclear program. President Barack Obama also raised Levinson’s case in his phone call with Rouhani in September – the highest level contact between the two countries in 34 years.

On Tuesday, both the White House and the State Department reiterated demands that Levinson be released.

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“As we approach the upcoming holiday season, we reiterate the commitment of the United States government to locate Mr. Levinson and bring him home safely to his family, friends and loved ones,” the White House said in a statement.

Tuesday marked the 2,454th day of Levinson’s captivity. That surpasses Terry Anderson, the former Associated Press bureau chief in Beirut, who was held for six years and eight months.

Levinson’s eldest son, Dan, wrote in an essay in The Washington Post that the family “was given hope with Hassan Rouhani’s election as Iran’s president and Javad Zarif’s appointment as foreign minister.” He called the two Iranian leaders “well respected men committed to the goodwill of all human beings, regardless of their nationality.”

“Given the negotiations between the United States and Iran over Tehran’s nuclear program, we particularly hope that officials can use their ongoing contact to resolve my father’s case,” Dan Levinson wrote. “Doing so would show the world that our two countries can work together to resolve our differences and would demonstrate Iran’s willingness to help an average American family’s plight.”

Iran has never explicitly acknowledged holding Levinson, though state-run media have made mention of the case, suggesting official involvement in Levinson’s disappearance. Rouhani, like other Iranian officials, have denied personal knowledge of Levinson’s whereabouts.

“We are willing to help, and all the intelligence services in the region can come together to gather information about him to find his whereabouts. And we’re willing to cooperate on that,” Rouhani told CNN’s Christiane Amanpour in an interview.

In January, the Associated Press reported that U.S. officials have concluded that Iran’s intelligence service “was almost certainly behind the 54-second video and five photographs of Levinson that were emailed anonymously to his family.”

A photograph released by the family earlier this year shows Levinson dressed in an orange jumpsuit with unkempt hair and beard. His drawn face bears little resemblance to the smiling, rosy-cheeked man in old family photos.

In 2012, the FBI announced a $1 million reward for information leading to Levinson’s safe recovery and repatriation.

“Our family will soon gather for our seventh Thanksgiving without Bob, and the pain will be almost impossible to bear,” Levinson’s wife, Christine, wrote in a statement this week.

She ended with a direct message for her husband: “Bob, if somehow you see or hear these words: Stay strong. You have a new grandson, just a month old. We can’t wait for you to meet him. We love you and will never stop working to bring you home safely.”